title: Albumin-induced epithelial-mesenchymal transition and ER stress are regulated through a common ROS-c-Src kinase-mTOR pathway: effect of imatinib mesylate.
abstract: The epithelial-mesenchymal transition (EMT) and endoplasmic reticulum (ER) stress induced by urinary protein, particularly albumin, play an important role in tubulointerstitial injury. However, signaling pathways regulating both albumin-induced EMT and ER stress are not precisely known. We postulated that reactive oxygen species (ROS), c-Src kinase, and mammalian target of rapamysin (mTOR) would act as upstream signaling molecules. We further examined the effect of imatinib mesylate on these processes. All experiments were performed using HK-2 cells, a human proximal tubular cell line. Protein and mRNA expression were measured by Western blot analysis and real-time PCR, respectively. Exposure of tubular cells to albumin (5 mg/ml) for up to 5 days induced EMT in a time-dependent manner, as shown by conversion to the spindle-like morphology, loss of E-cadherin protein, and upregulation of α-smooth muscle actin mRNA and protein. Albumin also induced ER stress as evidenced by phosphorylation of eukaryotic translation initiation factor-2α and increased expression of GRP78 mRNA and protein. Albumin induced ROS, c-Src kinase, and mTOR as well. Antioxidants, c-Src kinase inhibitor (PP2), and mTOR inhibitor (rapamycin) suppressed the albumin-induced EMT and ER stress. Antioxidants and PP2 inhibited the albumin-induced c-Src kinase and mTOR, respectively. Imatinib suppressed the albumin-induced EMT and ER stress via inhibition of ROS and c-Src kinase. Imatinib also inhibited the albumin-induced mRNA expression of MCP-1, VCAM-1, transforming growth factor (TGF)-β1, and collagen I (α1). In conclusion, the ROS-c-Src kinase-mTOR pathway played a central role in the signaling pathway that linked albumin to EMT and ER stress. Imatinib might be beneficial in attenuating the albumin-induced tubular injury.
authors.affiliation: Department of Internal Medicine, Asan Institute for Life Sciences, College of Medicine, University of Ulsan, Seoul, Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Jai Won
authors.initials: JW
authors.lastname: Chang
authors.forename: Won Seok
authors.initials: WS
authors.lastname: Yang
authors.forename: Soon Bae
authors.initials: SB
authors.lastname: Kim
authors.forename: Su Kil
authors.initials: SK
authors.lastname: Park
authors.forename: Jung Sik
authors.initials: JS
authors.lastname: Park
authors.forename: Sang Koo
authors.initials: SK
authors.lastname: Lee
mesh_terms: D000418:Albumins / Q000378:metabolism*; D000975:Antioxidants / Q000494:pharmacology; D001549:Benzamides; D015153:Blotting, Western; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D019610:Cytoprotection; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D000091342:Endoplasmic Reticulum Chaperone BiP; D004847:Epithelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000068877:Imatinib Mesylate; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects* / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D019061:src-Family Kinases
chemical_list: D000418:Albumins; D000975:Antioxidants; D001549:Benzamides; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000068877:Imatinib Mesylate; C546842:MTOR protein, human; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D058570:TOR Serine-Threonine Kinases